Formed in West Virginia by the West Fork River and Tygart Valley River when they meet around Pleasent Valley and Fairmont, the Monongahela flows north going through Morgantown into Pennsylvania and east south of the Pitt. There it then combines with the Allegheny River to form the Ohio River. Its waters are highly radioactive, up to 600+ rads, making swimming a somewhat impossible task without succumbing to radiation poisoning; it is best to just take the bridge.
- The shoreline and water are much, much more irradiated than any body of water in the Capital Wasteland (around 350 on the river bank and around 500 in the water). Drinking the water yields another 150+ rads, but no health.
- Mona fell into the Monongahela River, causing her skin to be covered in peeling skin and lesions.